Permanent magnetic suspension with roller guides

Abstract: A lens for slidable adapting on a guide rod has a lens assembly means; and a permanent magnetic assembly means connected to the lens assembly, having a permanent magnet for applying a close-coupled magnetic force on the guide rod to hold the lens assembly means at a desired position along the guide rod. The permanent magnetic is V-shaped with a north pole, a south pole, and a recessed longitudinal channel in-between for receiving the guide rod in close proximity, and has a plurality of rotational guide bearing means, each rolling against an underside of the guide rod to guide the lens assembly as it is moved along the guide rod. The lens assembly means also has an aperture therein in which the guide rod passes through to secure the lens assembly from releasing from the guide rod when shock loading exceeds the closed-coupled magnetic attraction force.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention generally relates to a lens which is movably positioned along a guide rod, and in particular relates to a movably positioned lens having magnetic means for holding it in place on the guide rod. Description of the Prior Art Conventional guidance assemblies for optical or mechanical devices include guide rods and re-circulating linear ball bearings which must be heavily pre-loaded to provide precision play-free guidance. This results in high cost, requires high accuracy between mating parts, and includes relatively bulky components. Further, relatively high drive forces are typically needed to move the pre-loaded components. Such pre-loads are susceptible to change with temperature. In one typical use, a guidance assembly supports a lens for filming motion pictures which requires exceptionally accurate positioning to ensure very sharp images to film a master tape (from which all future tapes will be copied). The filming of a motion picture may subject the guidance assembly to extreme temperature variations, such as those in a desert or mountainous climate. The extreme temperature variations may cause difficulty in positioning the lens assembly and may cause movement due to expansion and contraction in a pre-positioned lens assembly. SUMMARY OF THE INVENTION The invention provides a lens assembly according to claim 1. In an embodiment, the permanent magnetic assembly has an aperture therein through which the guide rod passes to protect the lens assembly from falling off the guide rod when shock loading may exceed the closed-coupled magnetic attraction force. The invention provides accurate guidance to moving mechanical assemblies (e.g. moving elements in a zoom lens) while maintaining low resistance to the drive forces in the direction of motion. The invention provides a reliable and accurate guidance under extreme temperature variations by employing permanent magnetic attraction unchanged by lubricants or other physical conditions. The invention applies to electronic zoom lens. It also applies to any opto-mechanical, electro-mechanical or like devices where reliable athermal guidance is needed. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the invention when read in conjunction with the appended claims and drawing attached hereto. BRIEF DESCRIPTION OF THE DRAWING Figure 1, not drawn to scale, shows a movable lens arranged on guide rods according to the present invention. Figure 2, not drawn to scale, shows a cross-sectional view of the guide rod and the permanent magnetic assembly along lines 2-2 in Figure 1. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a movable lens assembly 2 arranged on guide rods 4 and 6. In one embodiment, the guide rods 4 and 6 are two hardened steel rods. The movable lens assembly 2 includes a lens cell 10 having a perimeter 10a with a permanent magnet assembly 12 arranged thereon at the top of the lens cell 10 as shown. A pre-loaded bearing 14 and guide bearing 16 are also arranged on the perimeter 10a of the lens cell 10 at a 90° angle with respect to the permanent magnetic assembly 12. The pre-load bearing 14 and guide bearing 16 cooperate with the guide rod 6 to further support and position the lens cell 10 along the guide rod 4. The permanent magnet assembly 12 has a permanent magnet 20 which provides a closed-coupled attractive magnetic force to support the lens assembly 2 to the guide rod 4. Magnetic force lines f1 and f2 illustrate the magnetic force applied to the guide rod 4 as a close-coupled attractive magnetic force. The permanent magnet 20, in the embodiment, is U-shaped, having a north pole 40 and a south pole 42, and having a V-shaped recessed longitudinal channel 44 placed in close proximity to the guide rod 4 on the permanent magnetic assembly 12 to attract the guide rod and hold it against the ball bearings. As shown in Figure 2, the north pole 40 and south pole 42 are disposed about the guide rod 4 with a small air gap or clearance 41, at an arc segment of α. In a preferred embodiment, α equals 60°. The permanent magnet assembly 12 in the preferred embodiment has four ball bearings 22, 24, 26 and 28 arranged in a V-shaped configuration on each side of the permanent magnet assembly 12 , as shown. The four ball bearings 22, 24, 26 and 28 provide guidance for the lens cell 10 by rolling against the underside of the guide rod 4. The four ball bearings 22, 24, 26 and 28 provide all supportive and guiding functions. As shown in Figure 2, the rotational guide bearings 24 and 26 are disposed about the guide rod, and contact it at an arc segment of β 1 and β 3 respectively with respect to the horizontal plane H of the guide rod 4, as shown. In a preferred embodiment, β 1 and β 3 = 30° and β 2 equals 120°. Preferably, the lens cell 10 is secured against shock loads that may exceed the close-coupled magnetic attraction forces f1 and f2 by means of a clearance aperture 30 passing through the assembly (nonmagnetic i.e. lens cell) 12 . The guide rod 4 is thus surrounded by the rest of the assembly 12 to retain the guide rod 4 and to prevent the lens from falling off the guide rod 4. In the embodiment, additional guidance must be provided by the pair of bearings 14 and 16 which cooperate with a second guide rod 6 in order to control rotation of the assembly out of the optical axes. The guide bearing 16 is mounted on a rigid shaft (not shown), and the pre-load bearing 14 is mounted on two spring rods (not shown) to provide pre-loading. The above- described system is "space efficient" and easily adaptable to different design applications. The aforementioned embodiments described admirably achieve the objects of the invention; however, it will be appreciated that departures can be made by those skilled in the art without departing from the scope of the invention which is limited only to the following claims.

Claims: A lens assembly (2) for slidably positioning a lens along a guide rod (4), comprising: a lens cell assembly (10); and a permanent magnetic assembly (12) connected to the lens cell assembly (10), having a permanent magnet (20) arranged to be juxtaposed in close spatial relationship to the guide rod (4) with minimum clearance (41) between guide rod (4) and magnet assembly (12) for applying a close-coupled magnetic force on the guide rod (4) to hold the lens cell assembly (10) at a desired position along the guide rod (4), and having a plurality of rotational guide bearings (22, 24, 26, 28), each guiding the lens assembly (2) as it is moved along the guide rod (4). A lens assembly (2) according to claim 1, wherein the permanent magnet has a north pole (40) and a south pole (42) arranged to be disposed adjacent the guide rod (4) and spaced apart from one another. A lens assembly (2) according to claim 2, wherein the permanent magnet (20) is U-shaped. A lens assembly (2) according to claim 2, the north (40) and south (42) poles form a longitudinal channel (44) arranged to correspond to the shape of the guide rod (4) for providing maximum attraction forces with minimum clearance (41) between guide rod (4) and magnet assembly (12) supporting the lens cell assembly (10) on the guide rod (4) through four rolling elements (22, 24, 26, 28). A lens assembly (2) according to claim 2, wherein the north (40) and south (42) poles form a longitudinal channel (44) which is V-shaped. A lens assembly (2) according to claim 2, wherein the north pole (40) and south pole (42) are arranged to attract the guide rod (4) at an arc segment of about 60°. A lens assembly (2) according to claim 1, wherein the permanent magnetic assembly (12) has a plurality of rotational guide bearings (22, 24, 26, 28), each being arranged to be disposed adjacent the guide rod (4) and to support it to guide the lens assembly (2) along the guide rod (4). A lens assembly (2) according to claim 7, wherein the rotational guide bearings (22, 24, 26, 28) are arranged to contact the guide rod (4) at an arc segment of about 120° with respect to the horizontal plane H of the guide rod (4). A lens assembly (2) according to claim 1, wherein the permanent magnet assembly (12) has a longitudinal clearance aperture (30) for the guide rod (4) to pass through for preventing the lens assembly (2) from breaking if the permanent magnet (20) releases from the guide rod (4) in the event of shock loading that may exceed the closed-coupled magnetic force. A lens assembly (2) according to claim 1, wherein the lens cell assembly (10) comprises a pair of rotational guide bearings (14, 16) arranged to cooperate with another guide rod (6). A lens assembly (2) according to claim 10, wherein one (16) of the rotational guide bearings of said pair is rigidly mounted, and the other (14) is resiliently mounted for providing pre-loading.

Inventors: DEVENYI GABOR, DEVENYI, GABOR
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1994
Main classification: G02B7
IPC codes: G02B7